Electrical distribution system components are designed to operate at the standard 60 Hz frequency. However, many loads found in industrial and residential facilities demand currents that are non-sinusoidal and may be mathematically represented as a Fourier series summation of a fundamental plus higher order harmonics. For example, switch mode power supplies found in computers and other office equipment draw highly non-sinusoidal currents rich in harmonics. Similarly, usage of adjustable speed drives (ASD) with rectifier and invertor circuits for induction motor speed control has contributed to much greater line current harmonic levels.
The presence of harmonic currents on electrical power lines is becoming a major problem for electrical power engineers. These currents are responsible for overheating transformers, circuit breakers, filters, and neutrals and other sometimes strange occurrences. Harmonic problems are, by their nature, non-local; the equipment or system damaged by harmonics may be some distance from the source of harmonics.
Detection, diagnosis, and mitigation of harmonic problems require specialized instrumentation to accurately assess the level of harmonics present in the system. Instrumentation available to field engineers is generally inadequate to perform any detection or assessment of harmonics. While harmonic analysis equipment is available commercially, it is expensive, bulky, and overly complex, which makes it inappropriate and frequently unavailable for the field engineer who is called upon to diagnose equipment failures. This lack of instrumentation leads to improper diagnosis of problems and failure to correct harmonic problems as they occur.
Currently several commercial vendors manufacture equipment for performing this type of analysis. The primary drawback of the equipment is that they are not designed for ease of use. As a primary diagnostic instrument, the harmonics detector should be carried by field personnel whenever diagnostic measurements are made on electrical power lines. Even if no specific problems are present, the instrument should be used in a preventive role, to determine if harmonic currents are present in excessive amounts in the system. However, the various instruments currently available share the following characteristics, which render their use unlikely:
These units have retail prices in the range of $1,000 to $10,000 and up. Instrumentation in this price range is not generally available to field personnel. PA1 These instruments are relatively larger (some are suitcase size and weigh 30 lbs) and inconvenient to transport; this renders it unlikely that they will be carried to the trouble site. PA1 While some allow for battery operation, many of them require AC power for operation, severely limiting their usefulness in the field, where 120 V outlets are seldom available at the trouble site. PA1 They are complex instruments and a significant investment of time is required to learn their operation and few personnel are knowledgeable in their use. In particular, field personnel generally lack the training to use the equipment effectively. PA1 Some require the use of a PC (personal computer) to analyze dafa.
For these reasons, the existing equipment is not carried by field personnel, and hence is not generally used for problem diagnosis and is seldom, if ever, used in a preventive maintenance manner.
There is therefore a need for a hand-held harmonics detector that solves the above problems.